A liquid crystal display apparatus includes a liquid crystal display panel which has a display surface on a front side, and a backlight unit which illuminates the liquid crystal display panel from a back side of the liquid crystal display panel.
Hereinafter, a case in which the liquid crystal display panel is disposed in a vertical position will be described.
Conventionally, an edge light type backlight unit has been proposed (see Japanese Patent Laid-Open Publication No. 2012-237826, which is hereinafter referred to as Patent Document 1). The edge light type backlight unit includes a light guide plate which is rectangular provided at a back side of the liquid crystal display panel through an optical sheet group, a reflection sheet provided at a back side of the light guide plate, and a light source disposed to face a lower end face of the light guide plate. The light source is formed by mounting a plurality of LEDs disposed apart from each other in a horizontal direction on one surface of an LED substrate.
A part of light emitted by the LEDs enters the light guide plate through a lower end face of the light guide plate. Another part of the light emitted by the LEDs is made incident on the reflection sheet. The light having entered the light guide plate is emitted from a front surface of the light guide plate. The light made incident on the reflection sheet is reflected toward the light guide plate. In this case, when the reflected light enters the light guide plate, this light is also emitted from the front surface of the light guide plate.
The light emitted from the front surface of the light guide plate enters the liquid crystal display panel through diffusion, light collection, or the like by the optical sheet group.
When the liquid crystal display panel is uniformly illuminated by the backlight unit, the display surface of the liquid crystal display panel becomes uniformly bright.
However, if variations are present in a distance between each LED and the light guide plate, an amount of light having entered the light guide plate from each LED becomes uneven. The reason is that the light emitted by the LEDs away from the light guide plate is unlikely to be made incident on the light guide plate compared to the light emitted by the LEDs near the light guide plate. Thereby, the light is likely to be unevenly emitted from the front surface of the light guide plate. As a result, not only illumination by the backlight unit becomes uneven, but also brightness of the display surface of the liquid crystal display panel becomes uneven.
Then, in the display apparatus (a ‘liquid crystal module’ in text thereof) described in Patent Document 1, a lower portion of the light guide plate is partially in contact with the LED substrate, such that the distance between each LED and the light guide plate is constantly maintained.